With the development in digital technologies for electronic devices in recent years, demands for a nonvolatile variable resistance element which has a greater capacity, higher writing and reading speed, and longer-life and which consumes lower power in writing have been increased, for storing data such as images. To meet such demands, efforts of miniaturizing flash memories using existing floating gates are said to have limitations.
A nonvolatile variable resistance element using perovskite material (Pr(1·x)CaxMnO3 [PCMO], LaSrMnO3 [LSMO], and GdBaCoxOy, [GBCO], for example) has been proposed as a first conventional technique that could possibly meet the above demands (refer to PTL 1). With this technique, voltage pulses (a short-duration waveform voltage) having different polarities are applied to the perovskite material to increase or decrease resistance values and the resistance values that change are associated with data, thereby storing the data.
There is also a nonvolatile variable resistance element which utilizes the characteristics of a film of transition metal oxide (NiO, V2O, ZnO, Nb2O5, TiO2, WO3, or CoO), that is, resistance values change when voltage pulses having different pulse widths are applied to the film of the transition metal oxide, as a second conventional technique that enables switching the resistance values to using a homopolarity voltage pulse (refer to PTL 2). In another implemented configuration of the variable resistance element using a transition metal oxide film, cross-point type memory arrays using a diode are stacked.